According to a conventional technique, when the data of a digital camera is transferred to a server, the data is divided and assigned to plural digital cameras; and each of the digital cameras transfers the assigned data to the server (see, e.g., Japanese Laid-Open Patent Publication No. 2007-66061).
According to another disclosed technique, during parallel processing by a distributed-memory computer for an inquiry to parallel databases, the amount of data transferred between nodes is reduced when an access to the database of another node occurs (see, e.g., Japanese Laid-Open Patent Publication No. 2007-531087).
A technique of realizing data communication to a remote terminal when only ad-hoc communication is available and a technique of enabling data to be transferred from the closest terminal when plural mobile terminals are present respectively having the requested data have been disclosed (see, e.g., Japanese Laid-Open Patent Publication Nos. 2007-336360 and 2004-64646).
However, if data is shared among plural mobile terminals (for example, mobile terminals A to C) using the conventional techniques, when the mobile terminal A would like to use data Db retained by the mobile terminal B, the data Db needs to be transmitted from the terminal B to the terminal A. Similarly, when the mobile terminal A would like to use data Dc retained by the mobile terminal C, the data Dc needs to be transmitted from the terminal C to the terminal A.
Therefore, when a user of the mobile terminal A would like to use the data Db and Dc, the user can not access the data Db and Dc of the mobile terminals B and C from the mobile terminal A and therefore, a problem arises in that the usability of the data sharing is low.
The low usability of the data sharing also occurs when the mobile terminal B uses data Da retained by the mobile terminal A and the data Dc retained by the mobile terminal C and when the mobile terminal C uses the data Da retained by the mobile terminal A and the data Db retained by the mobile terminal B.
When the data Da to Dc are present in a server, accessing the server through a mobile telephone network enables each of the mobile terminals A to C to download the data Da to Dc.
However, the bandwidth for a base station in the mobile telephone network is determined and is shared by mobile terminals connected to the base station. Therefore, the bandwidth used by each of the mobile terminals decreases as the mobile terminals connected to the base station increases. Thus, when all the data Da to Dc are downloaded by each of the mobile terminals A to C, a problem arises in that the download time period becomes long.
Consequent to the mobile terminals A to C each downloading all the data Da to Dc, when the total amount of the data Da to Dc is great, a problem arises in that the mobile terminals A to C cannot download the data Da to Dc due to insufficient memory capacity.